Aircraft, and particularly military aircraft, utilize various types of target tracking systems. Such systems used in conjunction with computers and servo control systems are used to automatically and continuously train the aircraft guns and/or cameras on the target.
One method utilized to provide target tracking data to an aircraft processor employs a linkage connected between the pilot's helmet and a reference point on the aircraft. The linkage has mounted therein a system of motion sensing resolvers which sense the motion of the pilot's head as he visually tracks the target and provides continuous target directional data to the aircraft computer. Such a system frees the pilot for other tasks inasmuch as his visual tracking of the target is all that is required, and this is accomplished by the linkage attached between the pilot's head and an input to the computer located in the airframe.
In such a target tracking system, the linkage must respond to the movement of the pilot's head in the azimuth and elevational directions for resolution by the resolvers to provide appropriate directional information. In addition the linkage must also give freedom of movement of the pilot's head in the longitudinal direction to provide complete freedom of movement of the pilot's head without impeding his freedom of motion.
Such longitudinal movement has been provided in the past by using a collapsing or telescoping tubular arrangement. Such systems are restrictive to movement in both the expanding and collapsing directions. In addition the amount such tubes may be collapsed or expanded is limited by the necessity of stacking with a resultant restriction on the extent of the pilot's movement in the longitudinal direction. Similarly, such arrangements are bulky and require a number of tube sections which must be specially made to provide the telescoping feature.
The present invention provides a linkage system between a pilot's helmet and a reference point on the aircraft which eliminates the above disadvantage and provides a linkage utilizing fewer parts which collapses to a smaller size and extends a greater distance and which uses fewer parts than the tubular arrangements discussed above. In addition the linkage of the present invention provides greater flexibility and resiliency of movement and is not unduely affected by torsional body movement or sudden longitudinal movements of the pilot's head.
The present invention contemplates a linkage providing unrestricted three dimensional movement of the pilot's head. More specifically, the present invention contemplates two or more prestressed metal tapes each having an end effectively connected to a pilot's helmet and its other end connected to a reel to permit the tape to be unwound thereon. In their longitudinally expanded condition, the tapes form a rigid tubular area which houses a wire which makes the electrical connection between direction sensing devices and the computer panel. One set of mechanical linkages is provided to respond to head rotational movement in the azimuth and elevational directions while a compensatory set of mechanical linkages are provided which compensate for pilot's body movement in the left-right or up-down directions.